Conversion of hydrocarbon oils



Feb. 13, 1934. L. c HUFF CONVERSION OF HYDROCARBON OILS Filed May 27,1932 FIG. 2

RECEIVER \NVENTOR LYMAN C. HUFF ATTORNEY FRACTIONATOR COOLER FURNACEFURNACE l Patented Feb. 13, 1934 UNITED STATES CONVERSION OF HYDROCARBONOILS Lyman 0. Hull, Chicago, Ill., assignor to Universal Oil ProductsCompany, Chicago, 111., a corporation of Delaware Application May 27,1932. Serial No. 613,876

6 Claims. (Cl. l96-58) This invention relates to the conversion ofhydrocarbon oils for the production of substantial yields of desirablelight products and refers more particularly to an improved method andmeans of preventing the accumulation of coke in the reaction chamber ofa cracking system.

A type of cracking system which has recently come into commercialprominence utilizes a reaction chamber maintained at superatmosphericpressure and a reduced pressure vaporizing chamber in series. It iscommon practice in this type of cracking system to spray the heated oilfrom the heating element of the system into the upper portion of thereaction chamber against the reaction chamber walls. This permits quickseparation of liquid and vaporous products, allowing the residual liquidto flow downward over the inner surface of the chamber walls while thevaporous products pass downward through the vapor space comprisingsubstantially the entire cross sectional area of the chamber. Bothvaporous and'residual liquid products are withdrawn from the lowerportion of the chamber and both or, when desired, only the residualliquid, are directed to the reduced pressure vaporizing chamber wherefurther vaporization of the residual oil is accomplished withoutsubstantial further conversion.

When the charging stock and conversion conditions employed are such thata sufiicient quantity of residual oil is formed to maintain a rapidlymoving film of oil on the walls of the reaction chamber the residual oilpasses rapidly through the chamber without being subjected to prolongedconversion time in the reaction zone and without excessive cokeformation in this zone. However, when such conditions do not exist andparticularly when relatively low boiling charging stocks are employedand the quantity of residual oil is not sufiicient to maintain apositive and rapid flow of liquid down the walls of the chamber, theincreased time to which this liquid is subjected to the conversionconditions obtaining in the reaction chamber may result in the formationof substantial quantities of coke or carbonaceous material which mayadhere to the walls of the chamber and/ormay be washed out with theliquid, tending to block or obstruct the passage of conversion productsfrom the reaction chamber to the vaporizing chamber.

It is the primary purpose of the present invention to avoid coking inthe high pressure reaction zone and/or in the'line leading from the highpressure reaction zone to the reduced pressure vaporizing zone of acracking system of the type described. This is accomplished by supplyingan additional quantity of liquid oil to the reaction chamber,introducing it into this zone in such a manner thatv it Will spread andflow downward over the inner surface of the walls of the chamber for thepurpose of maintaining a rapidly to moving film or body of oil on thereaction chamber walls, thus increasing the rate of flow of the totaloil body, including the residual oil resulting from cracking, andmaterially decreasing the time to which the residual oil is exposed toes heavy condensate separated from the vapors withdrawn from the reducedpressure vaporizing zone prior to their fractionation, residual oilwithdrawn from the vaporizing chamber and oil from an external sourcesuch as heavy gas oil. The

most suitable type of oil for this purpose is one 30 which will notreadily decompose or crack to form coke under the conditions to which itis subjected while in the reaction chamber but which preferably containsa substantial propor tion of material which will remain unvaporized asin the reaction zone.

By passing the washing oil over the walls of the chamber, instead ofspraying it through the vapor space of the chamber or commingling itwith the stream of heated oil entering the chamber, excessivecooling ofthe vaporous products in the reaction chamber is avoided so thatconversion of' the vaporous products may continue during their passagethrough this zone.

'When cooling of the residual oil is required, as

well as'dilution and hastening of its flow through the reaction zone,the washing oil may be cooled to the desired temperature prior to itsintroduction into the reaction chamber. Preferably, however, in order toinsure minimum cooling of the 10 vapors, the washing oil is heated,prior to its introduction into the reaction chamber. This practicepermits the use of a larger quantity of oil without obtaining any morecooling than would be obtained by a much smaller quantity of cooler oil,thus giving more dilution of the residual oil and hastening its flow.The washing oil may be introduced into the reaction chamber at atemperature, for example, of the order of 400 to 750 Obviously thedesired tempera- Specific examples of types of to lid til

true will vary with difierent types of washing oil as well as withdifferent operating conditions in the reaction chamber and the range oftemperatures mentioned is only arbitrary. However, the temperature towhich the washing oil is heated is in all cases below the temperaturewhich will cause cracln'ng of the particular oil used to form anyappreciable amount of coke under the conditions to which it issubsequently exposed in the reaction chamber.

A specific embodiment of the invention may comprise subjecting ahydrocarbon oil to conversion conditions in a heating coil, introducingthe heated materials into the upper portion oi an enlarged reaction zonewherein their liquid components flow downward over the walls of thevessel and wherefrom liquid and vaporous products are withdrawn to areduced pressure vaporizing and separating zone, subjectlug vapors tl.from to fractionation, returning refhnr cor nsate resulting from saidfractionation to the heating coil for further conversion, subjectingvapors from said fractionation to condensation, and collecting theresulting products, subjecting raw oil charging stool: for the system toindirect contact and heat exchange with vapors passing irom saidvaporizing zone to said iractionating zone and returning condensateresulting from said heat exchange to the upper portion of said reactionzone to increase the quantity or liquid passing downward over the wallsof said reaction vessel.

Fig. i or the attached diagrammatic drawing illustrates one specificform of apparatus incorporating the features of the present invention.Raw oil charging stock for the system may be supplied through line 1 andvalve 2 to pump 3 from which it may be fed through line l, valve 5, heatexchanger 6, line 7, line 8and valve 9 to heating element 10. It will beunderstood that, when desired, all or any portion or the raw oil may besupplied directly to heating element 10 or may be preheated by otherwell known means, for example by introducing it into tractionatingcolumn 2, although suchother means are not illustrated in the drawing.

Heating coil to is located in a furnace ll of any suitable form and theoil supplied thereto is heated to the desired conversion temperaturepreferably at a substantial super-atmospheric pressure. The heated oilis discharged through line 12 and valve 13 into reaction chamber 14,

which is also preferably maintained at a substantial super-atmosphericpressure. Non-vaporous residual oil may flow downward over the walls ofchamber is and is withdrawn from the lower portion thereof, togetherwith. vaporcus products, through line 16 and valve it to vaporizingcharm ber 18, which is preferably maintained at substantially reducedpressure relative to that em ployed in chamber l i and wherein vaporousand non-vaporous products are separated.

' Vapors from chamber 18 may pass through line 19 and valve 20 into heatexchanger fiwherein they are indirectly contacted with raw oil suppliedthereto, as already described, and wherein their heaviest components arecondensed. Materials irom chamber 18, remaining vaporized in heatexchanger 6, pass through line 21 into fractionator 22 wherein theirinsufficiently converted components are condensed, collecting as refluxcondensate in the lower portion of this zone to be withdrawntherefromthrough line 23 and valve 24 to pump 25 and supplied therefrom through ie B a d valve 27 to beat g coil to incense for further conversion. Whendesired, apart-ion or all of the reflux; condensate may be directed fromline 26 through line 28, valve 29, line i and valve 5 to heat exchanger6 together with any raw oil fed therethrough, as already described.

Vapors from fractionator 22 pass through. line 30 and valve ill to besubjected to condensation and cooling in condenser 32, distillate anduncondensable gas rrom. which. passes through line 33 and valve 3a to becollected in receiver 35. Uncondensablc gas may be released from thereceiver through line 36 and valve 3?. Distillate may be withdrawn fromthis zone to storage or elsewhere, as desired, through line 38 and valve39. A portion of the distillate from receiver may, when desired, berecirculated by well known means, not shown in the drawing, to the upperportion of tractionator 22 to assist fractionation of the vapors.

Residual oil may be withdrawn irom chamber 13 through line so and maywithdrawn, allor in part, from the system to storage or to any desiredfurther treatment through line and valve 42. v A portion or residual oilmay, when desired, be passed through valve do, in line so, to pumpit tobe fed therefrom through line we valve 46 into line 5'! and thence to raction charm her it, as will be later more fully described.

The heavy components or the vapors from chamber 18 which are condensedin heat ex= changer 6 are withdrawn from this aonethrough line 47 andmay be passed, all or in part,'through line aii and valve la baclr intovaporizing chamber 18 or, all or in part, through line so and valve v 51into fractionator 22. A portion or all. of this condensate may be passedthrough valve 53, in line d7, to pump 5% to be fed therefrom throughline 55 and valve 56 into line 5*! and t ience to reaction chamber is,as will be later described.

In a similar manner a portion or the raw oil charging stock for thesystem may be diverted from line 4i and supplied through line 58, valve59, into line 5'? and thence to chamber 1+1, as will be later described.Reflux condensate from tractionator' 22 may be diverted from line 26 andsup plied through line so, valve 61, into line 57 and. thence to chamberis in a manner to be later described.

Preheated raw oil'or preheated combined reed (raw oil and refluxcondensate) as the case may be, from heat exchanger 6 may be directedthrough valve 52, in line '3, into line 5'? and thence to reactionchamber is, as will be later described more fully.

It is also within the scope of the invention to introduce any suitableoil such as gas oil, topped crude, etc., from an external source or anysuit-= able relatively heavy liquid product from the same or anothercracking system through line so, valve and line 5'? for transmission tochamber la, as will be presently described.

It will be understood that any one or any combination of the materialsabove mentioned, namely, residual oil from chamber 18, condensate fromheat exchanger 6, row oil charging stool:

for the system, rellur; condensate from fractionator 22, preheated oilfrom heat exchanger 6 and oil from an external source, may be suppliedto the reaction chamber as a washing medium.

The oil or comrningled oils chosen as the wash ing medium may bedirected from line- 5? through line 66, valves 67, 68 and 69 intochamber it. Instead of feeding the washing oil into the upper portion orthe reaction chamber, as de Mil l it

scribed, it is within the scope of the invention to introduce the oiland spray it against the walls of the chamber at any other point in thechamber. This will be more fully described and illustrated in connectionwith Fig. 4 and line 80 having valve 81 illustrates means forintroducing the washing oil into the lower portion of the chamber. V

As already mentioned, the oil thus supplied to chamber 14 is preferablyintroduced into the reaction zone at a fairly high temperature in orderto avoid excessive cooling of the vaporous products in thereactionchamber. A heating coil 71, located in a furnace 72, of any suitableform, is provided for the purpose of heating the oil from line 57 to thedesired temperaturawhen such heating is required. The oil may besupplied, all or in any desired proportion, through valve '70, in line57, to heating coil 71 and is discharged therefrom through line 73 andvalve 74 into line 66 and thence to chamber 14.

It is possible that oils obtained from within the system to be used aswashing oil in chamber 14 may be at too high a temperature for thepurpose required. In this case and when otherwise desirable the washingoil may be cooled, prior to their introduction into the reactionchamber, in cooler 7'7, by means of diverting all or any portion of theoil from line 66 through line 75 and valve '76 into the coolerand thencethrough line '78 and valve 79 back into line 66 and to chamber 14.

Fig. 2, which is a fragmentary cross-sectional view of the upper portionof chamber 14, illus trates one manner in which the washing oil may besupplied to the upper portion of chamber 14, through line 66 to be therepreferably sprayed against the walls of the vessel by means of asuitable spray device, forexample, such as indicated at 82 while theheated oil from heating coil 10 is introduced through line 12 andsprayed against the walls of chamber 14 by means of a spreader flange,as indicated at 15. In this manner an increased quantity of oil is madeto flow downward over substantially the entire length of the innersurface of the walls of the chamber, thus decreasing the time which theresidual conversion products remain in this zone, as already explained.

Another method and means for introducing the heated oil from heatingcoil 10 and the washing oil into the upper portion of the reactionchamber 14 is illustrated in Fig. 3, in'which the line from heating coil10 is again indicated by the number 12, therecirculating line by 66 andthe spray, which in this case takes the form of a spreader flange,similar to number 15 in Fig. 2, is indicated at 83.

It is also within the scope of the invention to introduce the washingoil at any desired point in the reaction chamber and to more clearlyillustrate this feature Fig. 4 of the attached drawing illustrates acase in which the flushing and cooling oil is introduced into the lowerportion of the reaction chamber near the outlet of vaporous and residualliquid products from this zone.

Referring to Fig. 4, reaction chamber 14 is shown in fragmentarycross-section. The line 12 supplying heated oil from the heating elemententers the upper portion of chamber 14 and is pointed downward at thecentral portion of the chamber. The conversion products are removed fromthe bottom of chamber 14 through line 16 and the chamber may, asillustrated in this figure, be provided with a cone shaped outlet 86.

Line 80, as here illustrated, enters the lower portion of the chamberand terminates in a spray coil 84, of any suitable form, adjacent thelower head 85 of the chamber. By means of this arrangement the heavyliquid entering'chamber 14, through line 12, drops through the chamberat a rapid rate and is withdrawn through line 16, while the lightervaporous products pass more slowly through the chamber and are withdrawnthrough the same ,line. When this method of introducing and withdrawingmaterials from the reaction chamber is employed, the residual liquidwill splash against the walls of manway 8'7, outlet 86 and a portion ofthe lower head of the chamber 85 and this material tends to coke on thewalls and obstruct the outlet. By providing a spray, as indicated, forthe intro duction of washing oil, the walls of the chamber against whichthe residual oil splashes are continuously washed and the residual oilis rapidly removed from the reaction zone.

The oil thus supplied to chamber 14 may also serve as a protecting fluidor diluent for the residual oil to prevent its rapid conversion to cokeor carbonaceous material, particularly when the oil thus employed ismore refractory to cracking than the residual liquid conversionproducts. When cooling of the recirculated oil is employed it may alsoserve to decrease the temperature of the residual liquid conversionproducts in chamber 14 to prevent their conversion to coke. These latterfeatures are, however, auxiliary to the main purpose which is toincrease the quantity of oil flowing downward over the walls of thereaction chamber and thus decrease the time to which liquid residualproducts of the conversion are exposed to the conversion conditions inthe reaction chamber. It is worthy of emphasis, however, that the methodof passing the washing oil over the walls of the chamber, as provided bythe present invention, permits cooling of the washing oil andsubstantial cooling of the residual oil without substantial cooling ofthe vapors in the reaction chamber.

The features of the invention are applicable to any type of crackingsystem operated under any temperature and pressure conditions ranging,for example, from 800 to 1200 F, and from substantally atmosphericpressure to'super-atmospheric pressure as high as 2,000 pounds or moreper square inch. In the type of system illustrated and above described,however, the preferred operating conditions are 900 to 1000 F. orthereabouts in the heating coil with pressures ranging from 100 to 800pounds per square inch, more or less, at the outlet from the heatingelement and in the reaction chamber and with substantially reducedpressures ranging from substantially atmospheric to 100 pounds, orthereabouts, per square inch, in the vaporizing, fractionating,condensing and collecting portions of the system. It will be understood,however, that the principles of the present invention are not limited touse with any particular range of conversion conditions. It is one of thesalient features of the present invention, however, that highertemperatures may be safely employed in the heated oil entering thereaction chamber than when no provision is made for diluting and rapidlyremoving the residual oil from this zone.

As a specfiic example of the advantages of the features of the presentinvention let us first consider a cracking operation in an apparatussimilar to that illustrated in the drawing except that the principles ofthe present invention are not employed. The charging stock is a as" A.P. I. gravity Pennsylvania kerosene distillate which is subjected, inthe heating element, to'a temperature of approximately 935 F. A pressureof approximately 400 pounds per square inch is employed in the reactionchamber and a reduced pressure of approximately 50 pounds per squareinch is employed in the vaporizing chamber. This operation may yieldapproximately '73 percent of motor fuel of high antiknock value, about 7percent of heavy residual oil, approximately 650 cubic feet of gas perbarrel of charging stock and a total of approximately 20 percent, basedon the charging stock, of coke, gas and. unaccountable loss.

By recirculating to the upper portion of the reaction chamber, in themanner described, condensate from the heat exchanger, in an amount equalto approximately 30 percent by volume of the charging stock, at atemperature of approximately 700 F. and without materially altering theother operating conditions, a yield of better quality residual oilamounting to approximately 10 percent of the charging stock may beproduced with a corresponding decrease in the coke and gas formation.The yield and quality of the motor fuel remains substantially unchangedand the operating cycle may be increased by several days, due to theabsence of excessive coke formation on the walls of the reaction chamberand/or in the line between the reaction chamber and vaporizing chamber.

It will be understood that the foregoing example is only illustrativeand does not limit the invention to the conditions or advantagesmentioned.

I claim as my invention:

1. In a cracking process of the character wherein hydrocarbon oil isheated to cracking temperature under pressure while flowing in arestricted stream through a heating zone, thence discharged into theupper portion of an enlarged vertical reaction zone maintained undercracking condi tions of temperature and pressure, both vapors andunvaporized oil passed downwardly through the reaction zone wherebyconversion of the va pors occurs in the reaction zone, and the vaporsand unvaporized oil are withdrawn from the lower portion of the reactionzone; the improvement which comprises passing a washing oil, other thansaid unvaporized oil. downwardly over neeaass the inner surfaces of thereaction zone, the washing oil being at an elevated temperature such asto prevent substantial cooling of the vapors whereby the conversion ofthe vapors in the reaction zone is not interfered with but said elevatedtemperature being insufilcient to cause substantial coking of thewashing oil in the reaction zone.

2. In a cracking process of the character where-= in hydrocarbon oil isheated to cracking temperature under pressure while flowing in arestricted stream through a heating zone, thence discharged into theupper portion of an enlarged vertical reaction zone maintained undercracking condl= tions of temperature and pressure, both vapors andunvaporized oil passed downwardly through the reaction zone wherebyconversion of the vapors occurs in the reaction zone, and the vaporsandunvaporized oil are withdrawn from the low er portion of the reactionzone; the improvement which comprises passing a washing oil, other thansaid unvaporized oil, downwardly over the inner surfaces of the reactionzone, the washing oil being introduced to the reaction zone at atemperature of the order of 400 F. to 750 Tr. whereby substantialcooling of the vapors and substantial 1W coking of the washing oil inthe reaction zone are prevented.

3. The process as definedin claim 1 further characterized'in that theunvaporized oil withdrawn from the reaction zone is flashed distilled bypressure reduction and resultant residual oil utilized as said washingoil.

4. The process as defined in claim 1 further characterized in that thevapors withdrawn from the reaction zone are cooled and resultant conllii densate utilized as said washing oil.

5. The process as defined in claim 1 further characterized in that thevapors withdrawn from the reaction zone are cooled and thenfractionated, the heavier condensate formed by the initial lli coolingbeing utilized as said washing oil and the lighter condensate formed bythe fractionation being supplied to the heating zone.

6. The process as defined in claim 1 further characterized in that saidwashing oil comprises at least a portion of the raw charging oil for thecracking process.

LYMAN c. HUFF.

